Lack of a systematic sustained effect of prolonged exercise bouts on resting metabolic rate in fasting subjects

Resting metabolic rate (RMR) and respiratory quotient (RQ) were measured in nine young men of normal weight after an overnight fast on three occasions, twice with and once without exercise on the previous evening. Exercise was cycling for 90 min at 100 W or 175 W. A Latin-square experimental design was used to balance the order of treatment with the type of treatment. Energy expenditure was measured by indirect calorimetry using a ventilated hood system. No significant after-effect of exercise on RMR was found: on the 100 W treatment the RMR had decreased by 0.04 +/- 0.06 kJ/min from the control value (4.68 +/- 0.13 kJ/min), and after the 175 W treatment it had increased by 0.11 +/- 0.08 kJ/min. On the 175 W exercise treatment RQs decreased significantly from 0.85 +/- 0.01 (control) to 0.82 +/- 0.01 (P less than 0.05). This indicates that single bouts of prolonged exercise can have a persisting effect on the type of substrate oxidized in the fasting state.